All Pinocchio had to do to change his nose was tell a lie or two. For the rest of us, nasal evolution has been a bit more complicated. According to a recent study by Pennsylvania State University researchers published in the journal PLOS Genetics, climate is one of the driving forces behind how this noticeable facial feature has changed over time.
"An important function of the nose and nasal cavity is to condition inspired air before it reaches the lower respiratory tract," the study authors write. "For this reason, it is thought the observed differences in nose shape among populations are not simply the result of genetic drift, but may be adaptations to climate."
To prove whether climate affects nose shape, the researchers evaluated the noses of several thousand participants from specific geographic backgrounds (West African, East Asian, South Asian and Northern European). They used a 3-D camera to create models, which allowed them to measure and compare the size and shape of the nares (which you know better as nostrils) and alar (outer nostril wall) base width. Basically, they wanted to determine if something other than standard, expected genetic drift could be causing nose differences across populations and geography.
People of South Asian, East Asian and West African descent tend to have greater alar base width and nares width than their European counterparts. East Asians typically sport the smallest noses, while protrusion of the nasal tip tends to be greater among Northern Europeans than any other group. "We measured a bunch of aspects of the nose. Nasal protrusion, heights of the nose, length of nasal ridge, etc.," says lead study author Arslan Zaidi. "Out of all of them we found that only the width of the nose is the one that seems to be varying more across population than explained by evolutionary chance."
Zaidi, senior author Mark Shriver, and the other scientists then looked at whether the nose width trait has a pattern across the globe that corresponds with humidity and temperature. "We tested for climate, temperature and humidity and we found there to be significant association with nostril width," he says. "So, people who live in colder, drier climates have narrower nostrils. And people in warm, humid claims have wider nostrils." These aren't exactly millennial developments, however. "These are patterns that we are detecting that are pre-recent movements. Presumably this signal of selection occurred tens of thousands of years ago."
Despite the seeming correlation between nose shape and climate, it's hardly the only driving factor. "It's one of many factors. It's a very complex history. It is significant, but it doesn't automatically imply causation," Zaidi says, adding that long-ago migration and even sexual selection could have played major parts. "Differences could have been driven by cultural preferences. Were wider noses more attractive to people in regions where it's warmer and vice versa? Purely speculative of course, but might be something to that."
Why all the fuss about noses? The study brings light to a couple of significant medical considerations. "A vital function of the nose is to warm inspired air to core body temperature and saturate it with water vapor before it reaches the lower respiratory tract," they write in the study. If that doesn't happen as it should, "low humidity in the respiratory tract leads to impaired mucociliary [combination of mucus and cilia] function and increases the risk of both upper and lower respiratory tract infections."
For the many people who live far away from the area/climate that their noses were evolved to be suited for, it's possible that they could wind up more susceptible, and ill-equipped to handle respiratory issues. This isn't the first time people have faced unexpected health risks when presented with a climate their genes and evolutionary history weren't set up to handle. For example, light-skinned people are at a significantly greater risk of skin cancer, sunburn and other concerns when exposed to high ultraviolet rays, as opposed to longtime residents whose skin has adapted appropriately through evolution.
Of everything revealed by the study, one finding especially stands out to the researchers. "It's important to remember that there are more similarities than differences. In all the traits we studied there is only one that is different — nose width," Zaidi explains. "The social consequences of this are far reaching. There aren't many differences between populations — there are more differences within populations, and we tend to forget that, on both genetic and phenotypic levels."